Headscale, for one. This is probably implied as part of one of your above stacks, but let's list it out loud. Tailscale is great and all, but it's downright icky to offload routing of any variety to a third party.
Immich. Turn off Apple or Google's automatic scraping of all photos, keep usability. Even if you're not a photo person, at least some of your users are.
Syncthing is or Nextcloud, or something in the family. This may already be part of your NAS plans.
One of the code forges like forgejo, gitea, gitlab. Even when not a developer. Self hosting involves configuration and if you can get that into text and into a history, it makes things so much easier. Add bells and whistles to your hearts content, but these are good suites for a lot of functionality. Forgejo does have federation on its road map, but it's a while off still.
These are ones I find pretty ubiquitous. There's so many options once you have initial infrastructure. Email, for instance, isn't as daunting as the horror stories make it sound, though not as simple as many hope. My suggestion is to take time and do it correctly. There's a lot of backtracking involved as you learn more, but it's usually worth it. Best of luck!